The implications of the minor ECG abnormalities that I have dealt with may be categorized as follows. Innocent: 1. Sinus arrhythmia, with or without nodal escape beats 2. Atrial extrasystoles 3. Incomplete right bundle-branch block 4. Parabolic depression of the ST segment in association with a rapid heart rate 5. Elevation of the ST segment in the right precordial leads 6. Positive/negative T waves in the transitional zone. Not necessarily indicating disease: 1. Ventricular indicating disease: 1. Ventricular extrasystoles 2. Complete right bundle-branch block 3. Left anterior or posterior hemiblock 4. Abnormally directed T-wave vectors. Probably indicating disease: 1. Plane or downward-sloping ST depression, at rest or on exercise, of more than 1 mm 2. Pyramidal arrowhead T waves, with or without an abnormally directed T-wave vector 3. Negative/positive T waves in leads facing the left ventricle 4. Inverted U waves. It is clear that careful assessment must be made before minor ECG abnormalities in presumptively normal individuals are accepted as indicators of the presence of heart disease.